build: support auto release type in publish script

---
type: pre_commit_static_analysis_report
description: Results of running static analysis checks when committing changes.
report:
  - task: lint_filenames
    status: passed
  - task: lint_editorconfig
    status: passed
  - task: lint_markdown
    status: na
  - task: lint_package_json
    status: na
  - task: lint_repl_help
    status: na
  - task: lint_javascript_src
    status: passed
  - task: lint_javascript_cli
    status: na
  - task: lint_javascript_examples
    status: na
  - task: lint_javascript_tests
    status: na
  - task: lint_javascript_benchmarks
    status: na
  - task: lint_python
    status: na
  - task: lint_r
    status: na
  - task: lint_c_src
    status: na
  - task: lint_c_examples
    status: na
  - task: lint_c_benchmarks
    status: na
  - task: lint_c_tests_fixtures
    status: na
  - task: lint_shell
    status: na
  - task: lint_typescript_declarations
    status: passed
  - task: lint_typescript_tests
    status: na
  - task: lint_license_headers
    status: passed
---

Author: Planeshifter

lib/node_modules/@stdlib/_tools/scripts/publish_packages.js

@@ -40,6 +40,7 @@ var readFileSync = require( '@stdlib/fs/read-file' ).sync;
 var readJSON = require( '@stdlib/fs/read-json' ).sync;
 var existsSync = require( '@stdlib/fs/exists' ).sync;
 var hasOwnProp = require( '@stdlib/assert/has-own-property' );
+var objectKeys = require( '@stdlib/utils/keys' );
 var contains = require( '@stdlib/assert/contains' );
 var memoize = require( '@stdlib/utils/memoize' );
 var repeat = require( '@stdlib/string/repeat' );
@@ -59,6 +60,8 @@ var namespaceDeps = require( '@stdlib/_tools/pkgs/namespace-deps' );
 var depList = require( '@stdlib/_tools/pkgs/dep-list' );
 var name2standalone = require( '@stdlib/_tools/pkgs/name2standalone' );
 var generateChangelog = require( '@stdlib/_tools/changelog/generate' );
+var recommendVersionBump = require( '@stdlib/_tools/changelog/recommend-version-bump' );
+var parseCommits = require( '@stdlib/_tools/changelog/parse-commits' );
 var toposort = require( '@stdlib/_tools/pkgs/toposort' ).sync;
 var ENV = require( '@stdlib/process/env' );
 
@@ -345,6 +348,88 @@ var memoizedNPMversionForDevDeps = memoize( npmVersion );
 
 // FUNCTIONS //
 
+/**
+* Returns the date of the latest npm release for a package.
+*
+* @private
+* @param {string} pkg - package name
+* @returns {(string|null)} ISO date string or null
+*/
+function getLatestReleaseDate( pkg ) {
+	var latestDate;
+	var versions;
+	var command;
+	var version;
+	var result;
+	var date;
+	var map;
+	var i;
+
+	command = 'npm view ' + pkg + ' time --json';
+	try {
+		result = shell( command ).toString();
+		map = JSON.parse( result );
+		latestDate = null;
+		versions = objectKeys( map );
+		for ( i = 0; i < versions.length; i++ ) {
+			version = versions[ i ];
+			if (
+				version !== 'created' &&
+				version !== 'modified' &&
+				version !== 'unpublished' &&
+				semver.valid( version ) &&
+				!semver.prerelease( version )
+			) {
+				date = new Date( map[ version ] );
+				if ( !latestDate || date > latestDate ) {
+					latestDate = date;
+				}
+			}
+		}
+		return ( latestDate ) ? latestDate.toISOString() : null;
+	} catch ( error ) {
+		debug( 'Encountered an error when attempting to retrieve release dates for package `%s`: %s', pkg, error.message );
+		return null;
+	}
+}
+
+/**
+* Determines the release type automatically based on commits since the last release.
+*
+* @private
+* @param {string} pkg - package name (without @stdlib/ prefix)
+* @returns {(string|null)} release type (`minor`, `patch`) or null if no release needed
+*/
+function determineAutoReleaseType( pkg ) {
+	var latestReleaseDate;
+	var standalonePkg;
+	var commitOpts;
+	var commits;
+	var bump;
+
+	standalonePkg = name2standalone( '@stdlib/' + pkg );
+	latestReleaseDate = getLatestReleaseDate( standalonePkg );
+
+	commitOpts = {
+		'dir': join( mainDir, 'lib/node_modules', '@stdlib', pkg )
+	};
+	if ( latestReleaseDate ) {
+		commitOpts.flags = {
+			'after': latestReleaseDate
+		};
+	}
+	commits = parseCommits( commitOpts );
+
+	// Determine the recommended version bump:
+	bump = recommendVersionBump( commits );
+
+	// Cap major bumps to minor (we don't want to increase major release line for now):
+	if ( bump === 'major' ) {
+		bump = 'minor';
+	}
+	return bump;
+}
+
 /**
 * Returns a cron schedule for a given package.
 *
@@ -695,7 +780,18 @@ function publish( pkg, clbk ) {
 		return invokeCallback( null, 'skipped' );
 	}
 
-	if ( flags[ 'release-type' ] ) {
+	if ( flags[ 'release-type' ] === 'auto' ) {
+		// Case: auto-determine release type based on commits...
+		releaseType = determineAutoReleaseType( pkg );
+		if ( releaseType ) {
+			changelog = generateChangelog( '@stdlib/'+pkg, {
+				'releaseType': releaseType
+			});
+		} else {
+			// No release needed, generate changelog without release type...
+			changelog = generateChangelog( '@stdlib/'+pkg );
+		}
+	} else if ( flags[ 'release-type' ] ) {
 		// Case: release type specified, so we generate a changelog for the specified release type...
 		changelog = generateChangelog( '@stdlib/'+pkg, {
 			'releaseType': flags[ 'release-type' ]
@@ -1087,7 +1183,7 @@ function publish( pkg, clbk ) {
 
 	// Write the current date to the `.keepalive` file...
 	if ( flags[ 'keep-alive' ] ) {
-		fs.writeFileSync( join( dist, '.github', '.keepalive' ), new Date().toISOString() + '\n' );
+		fs.writeFileSync( join( dist, '.github', '.keepalive' ), new Date().toISOString() + '\n' ); // eslint-disable-line no-restricted-syntax
 	}
 
 	fs.copyFileSync( join( __dirname, 'templates', 'CODE_OF_CONDUCT.md.txt' ), join( dist, 'CODE_OF_CONDUCT.md' ) );